Let me ruin your impression:
The dating sim world is buggy with a minor character suddenly go against his design. With this, he rise to prominence and topple the self-aware protagonist to get to MC status. Despite the self-correcting measure the World employed to deal with this abnormality, our minor character still become a harem master with a dense head.

He not dense, with main interest he unable to take steps forward since they status to fall apart and second main interest just like that
MC just straight minded idiot but he not dense since he aware of his feeling

Nah it’s totally a harem. But, it’s done in a fashion where it’s not “all about” the harem. There are several girls in the story that like our MC but, it’s more about his journey to becoming a Dragoon. With some intense “fluffiness” action XD

Really? I mean, I’m all for that. I like my harem as a side dish, and not the focus, lest it devolves into waifu wars that tend to leave most people unsatisfied. This is exactly how I like harems: there, but not taking the spotlight. It’s all about execution in the end, though.

“Rudel Arses” the first born of one of the ‘Three Lords’ of the Courtois Kingdom is from a corrupted family but at 5 years old he saw a dragon in the sky and his dark future as a villian changed. He was considered an idiot but was that true? how would his efort to became a dragoon change the kingdom?

His family and servant dont care about him and his half sister “Lena” and only ignored them ,only looking and doting on the second child “Chlust”and his other sister from the same mother “Erselica ”

Not that my seal of approval is worth much but this certainly has it. A one word summary of this is “earnest”. It is to the point and “pure” in how it captures the reader. Yet it still has some level of depth in the human interactions.

They must find the Legend Dragon….the strongest and final boss of the labyrinth

The Legend Dragon might have been reborn in Rudel’s world, give him a chance to show his greatness….if he’s paired with Rudel, he might be able to redeem his honor. Besides, there are no ‘ancestors’ here hahaha

So? Who did Rudel end up with? Is it a harem ending with Izumi,Millia,Fina,Sophia,Enora,Cattleya,Lilim,some far a way princess(raw),etc. (i forgot the other girls name)? If possible i want it to be like that. I mean there’s a lot of girls who likes him yet he will only choose one? I will feel sorry for Millia who likes him since the beginning of the STORY. And what’s more he’s a Duke so having multiple wives isn’t a problem.